AMP‐activated protein kinase inhibits TGF‐β‐induced fibrogenic responses of hepatic stellate cells by targeting transcriptional coactivator p300

Abstract

Liver fibrosis is a common consequence of various chronic liver injuries, including virus infection and ethanol. Activated hepatic stellate cells (HSCs) contribute to liver fibrosis through the accumulation of extracellular matrix proteins, including type I alpha collagen (COL1A). The activation of adenosine monophosphate-activated protein kinase (AMPK) modulates HSCs activation, but its underlying mechanism remains unclear. Here, we report that AMPK inhibits transforming growth factor (TGF)-β-induced fibrogenic property of HSCs by regulating transcriptional coactivator p300. We treated human (LX-2) and rat (CFSC-2G) HSC lines with TGF-β to induce fibrogenic activation of HSCs. Pharmacological activation of AMPK by treatment with 5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR), metformin, or adiponectin lowered TGF-β-induced expression of COL1A and myofibroblast marker alpha-smooth muscle actin (α-SMA). Transient transduction of constitutively active AMPKα (caAMPKα) was sufficient to attenuate COL1A and α-SMA expression, whereas an AMPK inhibitor considerably abrogated the inhibitory effect of AICAR on fibrogenic gene expression. Although AMPK significantly suppressed Smad-dependent transcription, it did not affect TGF-β-stimulated phosphorylation, nuclear localization, or DNA-binding activity of Smad2/3. AICAR rather attenuated TGF-β-induced Smad3 interaction with transcriptional coactivator p300 accompanying with reduction of Smad3 acetylation. Moreover, AICAR induced not only physical interaction between AMPK and p300 but also proteasomal degradation of p300 protein. Our data provide substantial evidence that AMPK could be a novel therapeutic target for treatment of liver fibrosis, by demonstrating the underlying mechanism of AMPK-induced antifibrotic function in HSCs.

Perilipin 5 restores the formation of lipid droplets in activated hepatic stellate cells and inhibits their activation

“…59 Recent studies indicated that activation of AMPK markedly attenuated TGF-β1 functions, 60 and interrupted the TGF-β signaling pathway by regulating transcriptional coactivator p300 in HSC. 61 Additional experiments are ongoing to further explore the impact of AMPK-caused phosphorylation of Plin5 on the protein-protein interaction between Plin5 and ATGL or abhd5, and its role in the reduction of lipolysis in HSC.…”

AMPK Inhibits the Stimulatory Effects of TGF-βon Smad2/3 Activity, Cell Migration, and Epithelial-to-Mesenchymal Transition

“…Recent studies have shown that AMPK inhibits the TGF-b signaling pathway (Mishra et al, 2008;Fisslthaler and Fleming, 2009;Cufi et al, 2010;Xiao et al, 2010;Lim et al, 2012). In addition, AMPK inhibits cancer cell migration and EMT via both TGF-b-dependent and -independent mechanisms (Cufi et al, 2010;Xiao et al, 2010;Lim et al, 2012;Chou et al, 2014;Wang et al, 2014;Zhang et al, 2014;Thakur et al, 2015;Yan et al, 2015).…”

Human Osteoblast Growth and Maturation in Response to Metformin and the Thienopyridone, A769662

“…Complex I is critical for reduced NADH to maintain the mitochondrial proton gradient necessary for ATP production, therefore inhibition of complex I, by Met, leads to a reduction in overall cellular energy charge [10]. This would seem at odds with a pro-anabolic action of Met reported for murine and rodent osteoblasts; AMPK activation in response to Met would lead to a decline of energy consumption, i.e., anabolism, with a paralleled increase in energy production [36] and there is certainly evidence that Met can inhibit collagen synthesis in human hepatic stellate cells [37]. It is unlikely therefore that AMPK-activating agents, including Met, will promote the synthesis of bone matrix, a composite of type I collagen impregnated with hydroxyapatite.…”